This relates to navigational tools to facilitate the comparison of two temporally related medical images on a computer-driven display. The term medical images is used broadly herein to refer not only to actual images such as x-rays, CT axial sections, MRI images, sonograms, mammograms and the like, but also to representations and/or abstractions of such images as in the case of a display of regions of interest on an anatomical background map. The invention is particularly useful in the comparison of chest computer tomography (CT) scans of the same patient taken at different times and will be described in that context. The principles of the invention may, however, be applied in the comparison of any two medical images of the same features.
It is common clinical practice to acquire chest CT scans of the same patient at different times and compare them to monitor nodular structures. By comparing the potentially pathological nodular structures present in these scans, vital diagnostic/treatment information can be obtained.
In today's clinical practice, the tracking and comparing of nodules across multiple temporal CT scans is a very tedious process. Modern CT scans produce image stacks of hundreds of axial image slices. While numerous tools exist for matching the major anatomical features of the lungs that are visible in both stacks, it is extremely time-consuming to find and match the corresponding nodules in the two stacks of hundreds of axial slices.